1. Field of the Invention
The present invention relates in general to azo-metal complex dye and method for producing the same and its use for a high density optical disc recording medium. In particular, the present invention relates to the azo-metal complex dyes which have strong absorption in the visible light region from 400 nm to 700 nm, light and thermal stabilities and dissolubility for organic solvent, and are suitable for producing high density optical disc recording medium.
2. Description of the Related Art
With the progress of generation, a great quantity of information is in circulation, but the traditional magnetic disc recording medium cannot satisfy the trend. Therefore, a recording medium with high density in storage, miniaturization and lower cost is needed, and the optical disc recording medium is developed. Recently, the functional pigments with the combination of organic synthesis chemistry and photochemistry have been used in several industries, such as non-linear optical elements, optical disc recording medium, photoresist, thermal/light/electric sensors and detectors, energy transfer and storage, medical treatment and organism.
In 1981, Law et al. applied 3,3xe2x80x2-diethyl-12-acetyl-thiotetracyanine perchlorate, a kind of cyanine dye, in the fabrication of the optical disc first (see K. Y. Law, P. S. Vincett, and G. E. Johnson, Appl. Phys. Lett., 39, 718 (1981)). These kinds of dyes were chosen for the reason that they match the near IR laser pickup head. Its manufacturing method is mixing a cyanine dye with PVAc, then coating the mixture on the substrate by spin coating to form an optical disc. With the success in applying the cyanine dye in optical memory material, different kinds of dyes are developed to use as the optical memory material, such as disclosing in JP 072254167, 09193545, 09194545, 09226250, 09274732, 10044066, 11310728 and so on. The organic dyes are used as storage material because they can be coated on the substrate by simple spin coating. The manufacturing time is short and the cost is reduced as compared with the vacuum sputtering coating. Hence, the dissolubility in organic solvent and the stability of the organic dyes are important factors.
Therefore, the object of the present invention is to synthesize azo-metal complex dyes which have strong absorption in the visible light region from 400 nm to 700 nm, light and thermal stabilities and dissolubility for organic solvent, and are suitable for producing high density optical disc recording medium.
Azo-Metal Complex Dye
An azo-metal complex dye represented by the following formula (I) for a high-density optical disc recording medium: 
wherein
R1 is selected from the group consisting of C1-8 alkoxyl, carboxy, C1-8 alkyoxycarbonyl (xe2x80x94CO2R6) and amide (xe2x80x94CONR8R9);
R2, R3, R4 and R5 can be the same or different and are selected from the group consisting of hydrogen, C1-8 alkyl, C1-8 alkoxyl, carboxy, C1-8 alkyoxycarbonyl (xe2x80x94CO2R6), C1-6 alkylaminealkylenecarboxy (xe2x80x94CO2R7NR8R9), amide (xe2x80x94CONR8R9), nitro (xe2x80x94NO2), trifluoromethyl (xe2x80x94CF3), sulfonic acid fluoride group (xe2x80x94SO2F), sulfonic acid group (xe2x80x94SO3H) and halogen;
X is selected from the group consisting of carbon and nitrogen; and
M is selected from the group consisting of Mg+2, Mn+2, Co+2, Ni+2, Cu+2, and Zn+2.
If R1, R2, R3, R4 and/or R5 in formula (I) are/is C1-8 alkyoxycarbonyl (xe2x80x94CO2R6), R6 can be C1-8 alkyl.
If R2, R3, R4 and/or R5 in formula (I) are/is C1-6 alkylaminealkylenecarboxy (xe2x80x94Co2R7NR8R9), R7 can be C1-8 alkylene, R8 and R9 can be the same or different and can be hydrogen or C1-8 alkyl.
If R1, R2, R3, R4 and/or R5 in formula (I) are/is C1-8 amide (xe2x80x94CONR8R9), R8 and R9 can be the same or different and can be hydrogen or C1-6 alkyl.
Preparing of the Azo-Metal Complex Dyes
The azo-metal complex dye suitable for a high density optical disc recording medium represented by the following formula (I), 
and is producing by the following steps.
(a) proceeding a diazotization to modify an amine having the following formula (II) to a diazonium salt. 
(b) proceeding a coupling reaction to couple 2-amino-3-hydroxypyridine as shown in formula (III) with the diazonium salt in an organic solvent. 
(c) proceeding a chelating reaction with metallic salt of bivalence in an organic solvent.
In the above-mentioned formulas (I), (II) and (III), R1 can be C1-8 alkoxyl, carboxy, C1-8 alkyoxycarbonyl or amide; R2, R3, R4 and R5 are the same or different and can be hydrogen, C1-8 alkyl, C1-8 alkoxyl, carboxy, C1-8 alkyoxycarbonyl, C1-6 alkylaminealkylenecarboxy, amide, nitro, trifluoro-methyl, sulfonic acid fluoride group, sulfonic acid group or halogen; X can be carbon and nitrogen; and M can be Mg+2, Mn+2, Co+2, Ni+2, Cu+2 or Zn+2.
In the step (a), the diazotization can proceed by using one of two methods. The first method is reacting the amine with sodium nitrite (NaNO2) and acid to form the diazonium salt represented by the following formula (IV), and the reaction is as follows: 
The second method is reacting the amine with nitrosylsulfuric acid (HNOSO4) and acid to form the diazonium salt represented by the following formula (IV), and the reaction is as follows: 
No matter which methods are chosen, the acid can be H2SO4, HOAc, H3PO4 and C2H5COOH.
In the step (b), the obtained diazonium salt represented by the formula (IV) reacts with 2-amino-3-hydroxypyridine as shown in formula (III) to form the azo compound, and the coupling reaction is as follows: 
The organic solvent used in the coupling reaction can be C1-6 alcohol, dimethyl sulfoxide (DMSO), N,N-dimethyl formamide (DMF), diacetone alcohol (DAA) and tetrahydrofuran (THF).
In the step (c), the obtained azo compound represented by the formula (V) reacts with metallic salt of bivalence, MA2 or MB, in an organic solvent to form the azo-metal complex dye represented by the formula (I). If MA2 is chosen as the chelating agent, A can be OAcxe2x88x92, Clxe2x88x92, Brxe2x88x92, or acetylacetonate. If MB is chosen as the chelating agent, B can be Co3xe2x88x922 or SO4xe2x88x922.
Preparing of the High Density Optical Disc Recording Medium
The method for producing a high density optical disc recording medium, comprising the following steps:
(a) providing a first substrate;
(b) dissolving the azo-metal complex dye set forth in claim 1 in an organic solvent to form a solution, and coating the first solution on the first substrate;
(c) drying the solution to form an azo-metal complex dye layer;
(d) disposing a reflection layer on the azo-metal complex dye layer; and
(e) disposing a second substrate on the reflection layer
In the step (b), the organic solvent can be C1-6 alcohol, C1-6 ketone, C1-6 ether, halogen compound or amide. Wherein, C1-6 alcohol can be methanol, ethanol, isopropanol, diacetone alcohol (DAA), 2,2,3,3-tetrafluoropropanol, trichloroethanol, 2-chloroethanol, octafluoropentanol or hexafluorobutanol; C1-6 ketone can be acetone, methyl isobutyl ketone (MIBK), methyl ethyl ketone (MEK) or 3-hydroxy-3-methyl-2-butanone; the halogen compound can be chloroform, dichloromethane or 1-chlorobutane; and the amide can be dimethylformamide (DMF) or dimethylacetamide (DMA).
After the azo-metal complex dye is dissolved in the above-mentioned organic solvent, it is coated on the first substrate by, such as spray, roller, dip, spin coating and so on. Then proceeding the swing and dry processes on sequence to drive the organic solvent away, so as to form the azo-metal complex dye layer on the first substrate. Then, step (d) is follows.
In the step (d), the material of the reflection layer is such as Au, Ag, Al, Cu or Cr.
In the step (e), another second spare substrate is bonded with the first substrate which has the azo-metal complex dye layer and the reflection layer thereon to form the high-density optical disc recording medium. The bonding method may be one such as spin coating, printing, glue melting by heat and so on.
The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings, given by way of illustration only and thus not intended to be limitative of the present invention.